smart_ptr/detail/sp_counted_base_sync.hpp

0001 #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED
0002 #define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED
0003
0004 // MS compatible compilers support #pragma once
0005
0006 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
0007 # pragma once
0008 #endif
0009
0010 //  detail/sp_counted_base_sync.hpp - g++ 4.1+ __sync intrinsics
0011 //
0012 //  Copyright (c) 2007 Peter Dimov
0013 //
0014 //  Distributed under the Boost Software License, Version 1.0.
0015 //  See accompanying file LICENSE_1_0.txt or copy at
0016 //  http://www.boost.org/LICENSE_1_0.txt
0017
0018 #include <boost/smart_ptr/detail/sp_typeinfo_.hpp>
0019 #include <boost/config.hpp>
0020 #include <limits.h>
0021
0022 #if defined( __ia64__ ) && defined( __INTEL_COMPILER )
0023 # include <ia64intrin.h>
0024 #endif
0025
0026 #if defined(BOOST_SP_REPORT_IMPLEMENTATION)
0027
0028 #include <boost/config/pragma_message.hpp>
0029 BOOST_PRAGMA_MESSAGE("Using __sync sp_counted_base")
0030
0031 #endif
0032
0033 namespace boost
0034 {
0035
0036 namespace detail
0037 {
0038
0039 #if INT_MAX >= 2147483647
0040
0041 typedef int sp_int32_t;
0042
0043 #else
0044
0045 typedef long sp_int32_t;
0046
0047 #endif
0048
0049 inline void atomic_increment( sp_int32_t * pw )
0050 {
0051     __sync_fetch_and_add( pw, 1 );
0052 }
0053
0054 inline sp_int32_t atomic_decrement( sp_int32_t * pw )
0055 {
0056     return __sync_fetch_and_add( pw, -1 );
0057 }
0058
0059 inline sp_int32_t atomic_conditional_increment( sp_int32_t * pw )
0060 {
0061     // long r = *pw;
0062     // if( r != 0 ) ++*pw;
0063     // return r;
0064
0065     sp_int32_t r = *pw;
0066
0067     for( ;; )
0068     {
0069         if( r == 0 )
0070         {
0071             return r;
0072         }
0073
0074         sp_int32_t r2 = __sync_val_compare_and_swap( pw, r, r + 1 );
0075
0076         if( r2 == r )
0077         {
0078             return r;
0079         }
0080         else
0081         {
0082             r = r2;
0083         }
0084     }
0085 }
0086
0087 class BOOST_SYMBOL_VISIBLE sp_counted_base
0088 {
0089 private:
0090
0091     sp_counted_base( sp_counted_base const & );
0092     sp_counted_base & operator= ( sp_counted_base const & );
0093
0094     sp_int32_t use_count_;        // #shared
0095     sp_int32_t weak_count_;       // #weak + (#shared != 0)
0096
0097 public:
0098
0099     sp_counted_base(): use_count_( 1 ), weak_count_( 1 )
0100     {
0101     }
0102
0103     virtual ~sp_counted_base() // nothrow
0104     {
0105     }
0106
0107     // dispose() is called when use_count_ drops to zero, to release
0108     // the resources managed by *this.
0109
0110     virtual void dispose() = 0; // nothrow
0111
0112     // destroy() is called when weak_count_ drops to zero.
0113
0114     virtual void destroy() // nothrow
0115     {
0116         delete this;
0117     }
0118
0119     virtual void * get_deleter( sp_typeinfo_ const & ti ) = 0;
0120     virtual void * get_local_deleter( sp_typeinfo_ const & ti ) = 0;
0121     virtual void * get_untyped_deleter() = 0;
0122
0123     void add_ref_copy()
0124     {
0125         atomic_increment( &use_count_ );
0126     }
0127
0128     bool add_ref_lock() // true on success
0129     {
0130         return atomic_conditional_increment( &use_count_ ) != 0;
0131     }
0132
0133     void release() // nothrow
0134     {
0135         if( atomic_decrement( &use_count_ ) == 1 )
0136         {
0137             dispose();
0138             weak_release();
0139         }
0140     }
0141
0142     void weak_add_ref() // nothrow
0143     {
0144         atomic_increment( &weak_count_ );
0145     }
0146
0147     void weak_release() // nothrow
0148     {
0149         if( atomic_decrement( &weak_count_ ) == 1 )
0150         {
0151             destroy();
0152         }
0153     }
0154
0155     long use_count() const // nothrow
0156     {
0157         return const_cast< sp_int32_t const volatile & >( use_count_ );
0158     }
0159 };
0160
0161 } // namespace detail
0162
0163 } // namespace boost
0164
0165 #endif  // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_SYNC_HPP_INCLUDED